Regional Deposition of 3.6μm Particles in Subjects with Mild to Moderately Severe Asthma

ABSTRACT

Regional deposition of 3.6 μm (aerodynamic diameter) monodisperse Teflon particles labelled with ¹¹¹In was studied twice in ten mild to moderately severe asthmatics. The subjects inhaled the particles with maximally deep inhalations at 0.51/sec. Lung retention was measured after 0,6,24 and 48 hrs using a profile scanner equipped with two 13 x 5 cm NaI crystals. The retentions after 24 hrs (Ret₂₄) and 48 hrs (Ret₄₈) were highly correlated, r = 0.98. Also Ret₂₄ and Ret₆ were well correlated, r = 0.85. There was a significant negative correlation between Ret₂₄ and airway resistance (R_aw). Ret₂₄ tended to be lower in the asthmatics than in healthy subjects earlier studied at comparable R_aw -values. In contrast to an earlier similar investigation in healthy subjects there was a rather poor reproducibility of the Ret₂₄ values, also after standardizing for differences in R_aw (r = 0.58). The study indicates that regional deposition can be studied by measurements of lung retention after 24 hrs and probably also after 6 hrs in mild to moderately severe asthmatics. This means that repeated measurements can be performed within rather short time periods with very low radiation doses.